Thumbnail view not appearing in "Open Displays" on Windows

[lhsego]

On Windows, the thumbnail view of the display in "Open Displays" is blank (at least on Chrome, haven't tested it on Firefox).

[hafen]

Interesting... this shouldn't be a platform-specific problem unless it has to do with the generation of the thumbnail. Can you check to see if the thumbnail exists? Look for _vdb_directory_/displays/_group_/_name_/thumb.png.

Also, have you looked at it on mac/linux too? What kind of panel function is it? Thumbnails currently only work for panel functions that can create raster images (base R, ggplot, and lattice).

[lhsego]

It's happening with base R. On mac/linux, the thumb_small.png file gets created like this:

But on Windows, thumb_small.png is just a white, square, image:

[hafen]

Oh strange. I thought your fix took care of this?

[lhsego]

No, my fixes just ensured that vdb files actually got copied from the temp folder to the vdb because file.rename(), when applied to a directory, does nothing in Windows. The files have to be renamed individually (using a vector of filenames) in file.rename(). This issue is something else: thumb_small.png isn't getting written (or written correctly) in Windows. Will look into it.

[amwhite]

This is a known issue with the rasterImage function which is used to create the thumbnail. Basically it doesn't work if you're accessing a windows machine via remote desktop. See issue and potential solution (for windows server) here:
http://r.789695.n4.nabble.com/R-base-package-grid-does-not-output-raster-image-td4672188.html

[amwhite]

More information about my previous comment. The problem with rasterImage() and windows remote desktop is mentioned in the documentation here: https://stat.ethz.ch/R-manual/R-devel/library/graphics/html/rasterImage.html. It's important to note that the problem here is the remote desktop connection when creating the display (i.e. calling makeDisplay()) not when viewing the display.

When remoting from a windows machine to a windows machine, you can set the number of colors to Highest Quality (32 bit) like below and that alleviates the problem:

When remoting from mac to windows I tried setting colors to Millions instead of Thousands (Preferences-->Display before connecting to remote machine) but RDC just froze. I'm not sure RDC for Mac is stable/powerful enough to handle this but perhaps others should try.

[lhsego]

Thanks for figuring this out, Amanda!

[hafen]

I wonder if we should use something other than rasterImage. Originally I just made a scaled-down version of the image but had a hard time doing it reliably. Also, we don't have a good way to get thumbnails for javascript-based panel functions right now as they are rendered in the browser instead of R. This is extremely low priority to do anything about in my opinion.

[hafen]

Least we could do is make it show "no thumbnail available" when there isn't one.